Alves Lara C, Wood Chris M
McMaster University, Department of Biology, Hamilton, Ont., Canada L8S 4K1.
Aquat Toxicol. 2006 Jun 30;78(3):217-32. doi: 10.1016/j.aquatox.2006.03.005. Epub 2006 Mar 27.
This study examined the impact of elevated dietary Ca(2+) on the responses to chronic dietary Pb exposure in juvenile rainbow trout. Trout were fed reference (0.3microgPb/g, approximately 20mgCa(2+)/g) and Pb-enriched diets ( approximately 50 or 500microgPb/g) in the presence of background Ca(2+) ( approximately 20mgCa(2+)/g) or ( approximately 60mgCa(2+)/g) of added Ca(2+) (as CaCO(3)) for 42 days. The quantitative order of Pb accumulation in tissues reflected the exposure pathway of Pb via the diet (per tissue wet weight): gut>bone>kidney>liver>spleen>gill>carcass>brain>white muscle. The anterior intestine accumulated the most Pb per tissue wet weight, while the bone accumulated the most Pb per fish weight. Pb concentrations were much higher in the posterior kidney than the anterior kidney. Simultaneous addition of Ca(2+) to the diet had an overall protective effect in all the tissues analysed in reducing Pb accumulation. The RBCs accumulated 100 times more Pb when compared to the plasma, while the whole blood delta-aminolevulinic acid dehydratase was inhibited in the high treatment group without added Ca(2+), by the end of the exposure. Neither plasma Cl(-), K(+), Mg(2+) nor Na(+), K(+)-ATPase activities in the gills, mid- and posterior intestine were affected. However, there were mild disruptions in plasma Na(+) and Ca(2+) levels in the elevated Pb and Ca(2+) treatment groups, and a significant up-regulation in Na(+), K(+)-ATPase activity at the anterior intestine in fish fed the high Pb diets with background or added Ca(2+). By day 42, Pb levels in most tissues had either stabilized or started to decrease, indicating some capacity for regulation of accumulated loads. We conclude that elevated dietary Ca(2+) levels will be protective in reducing Pb burdens in freshwater juvenile rainbow trout exposed to environments contaminated with waterborne Pb.
本研究考察了日粮中钙（Ca²⁺）水平升高对幼年虹鳟鱼慢性铅暴露反应的影响。在日粮中添加碳酸钙使背景钙（Ca²⁺）水平维持在约20mgCa²⁺/g或添加额外的钙（Ca²⁺）使钙水平达到约60mgCa²⁺/g的条件下，让虹鳟鱼分别摄食对照日粮（0.3μgPb/g，约20mgCa²⁺/g）和高铅日粮（约50或500μgPb/g），持续42天。各组织中铅积累量的数量级反映了铅通过日粮的暴露途径（按组织湿重计）：肠道＞骨骼＞肾脏＞肝脏＞脾脏＞鳃＞鱼体＞脑＞白肌。按组织湿重计，前肠积累的铅最多，而按鱼体重计，骨骼积累的铅最多。后肾中的铅浓度远高于前肾。日粮中同时添加钙（Ca²⁺）对所有分析组织减少铅积累均具有总体保护作用。暴露结束时，与血浆相比，红细胞积累的铅多100倍，且在未添加钙（Ca²⁺）的高剂量处理组中，全血δ-氨基乙酰丙酸脱水酶受到抑制。鳃、中肠和后肠中的血浆氯离子（Cl⁻）、钾离子（K⁺）、镁离子（Mg²⁺）以及钠离子（Na⁺）、钠钾-ATP酶活性均未受影响。然而，在高铅和高钙处理组中，血浆钠离子（Na⁺）和钙（Ca²⁺）水平出现轻度紊乱，在摄食含背景钙（Ca²⁺）或添加钙（Ca²⁺）的高铅日粮的鱼的前肠中，钠钾-ATP酶活性显著上调。到第42天，大多数组织中的铅水平要么趋于稳定，要么开始下降，这表明机体具有一定调节铅累积量的能力。我们得出结论，日粮中钙（Ca²⁺）水平升高对于减少暴露于受水体铅污染环境中的淡水幼年虹鳟鱼体内的铅负荷具有保护作用。
